1. Field of the Invention
The present invention relates to a liquid discharge recording head for recording on a recording medium by discharging ink from the discharge port group provided for an orifice plate. The invention also relates to a method of manufacture therefor.
2. Related Background Art
A liquid discharge recording apparatus is such that, for example, ink is supplied to a liquid discharge recording head, and by driving ink droplet discharging means, such as piezoelectric elements or electrothermal converting elements provided for a liquid discharge recording head, in accordance with image data in order to form images on a recording sheet or some other recording medium by means of ink dot patterns. The ink discharge recording apparatus that performs recording by discharging ink from the discharge ports of the liquid discharge recording head is known as a recording apparatus having such excellent advantages as a lesser amount of noises, a capability of recording at high speed, among some others.
FIG. 67 is a perspective view which shows the conventional liquid discharge recording head in a state of partially broken in representation, and also, in a state where the orifice plate is separated. FIG. 68 is a perspective view which shows the liquid discharge recording head represented in FIG. 67 in a state where the orifice plate is bonded to it.
For the conventional liquid discharge recording head 315 of the kind, a heater board 301, having electrothermal converting elements (discharge heaters 301a) which are the elements that generate energy for discharging ink, and wiring for supplying electric power to the discharge heaters 301a formed on a silicon base plate using silicon film formation process, is set by means of die bonding on a supporting base (base plate 304) formed by aluminum, ceramics, or the like. The base plate 304 also functions as the heat sink that radiates heat generated on the heater board 301 along with the driving of discharge heaters 301a and cools it.
On the heater board 301, there is arranged the ceiling plate 305 that forms ink flow paths. The ceiling plate 305 is provided with the nozzles 307 which constitute ink flow paths communicated with the discharge ports 306a of the orifice plate 306 formed in a recess on the bottom face of the ceiling plate 305; the common liquid chamber 308 which serves as a sub-tank for supplying ink to the nozzles 307 each formed in a recess on the bottom face of the ceiling plate 305; and the ink supply port 309 through ink is supplied to the common liquid chamber 308.
Further, on the base plate 304, a chip tank 311 to form ink passage 311a to guide ink to the ink supply port 309 from an ink storage tank, or sub-tank, or the like (not shown) arranged on the upstream side of the liquid discharge recording head 315 in the ink flow direction.
A front plate portion 311b is formed on the surface to which the nozzles 307 of the chip tank 311 is open. The front plate portion 311b functions to bond and hold the orifice plate 306 having the discharge ports 306a open at the same intervals as those between nozzles 307 themselves on the circumferential area of the discharge ports 306a, and also, functions to support the orifice plate 306 so as to enable the orifice plate 306 to withstand sufficiently against the force exerted by the time of attachment or detachment, and the holding pressure exerted by the cap member (not shown) arranged for the recording apparatus main body at the time of capping operation.
Here, in the specification hereof, the structure of liquid discharge recording head which is in a state that the orifice plate is removed is called “recording head main body”.
In this respect, the ceiling plate 305 is formed by resin, such as polysulfone, polyether sulfone, polypropylene, denatured polyphenylene oxide, polyphenylene sulphide, or liquid crystal polymer or formed by such material as ceramics, silicon, nickel, or carbon.
Also, the orifice plate 306 is formed by metallic plate, such as SUS (stainless steel), Ni, Cr, or Al, or a resin mold, resin film material, or the like, such as polyimide, polysulfone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, or polypropylene, or further, formed by silicon, ceramics, or the like.
Now, the description will be made of the outline of assembling process of the liquid discharge recording head.
At first, the discharge heaters 301a on the heater board 301 set on the base plate 304 and the nozzles 307 of the ceiling plate 305 which is arranged relatively therefor are aligned to be in agreement in high precision, and using bonding means such as bonding agent or pressure means such as pressure spring (not shown) the heater board 301 and the ceiling plate 305 are kept closely in contact for the formation of ink flow paths.
Then, the chip tank 311 is incorporated on the base plate 304 to connect the ink supply port 309 of ceiling plate 305 with the ink passage 311a of chip tank 311. At this juncture, the front plate portion 311b of chip tank 311 covers the front end of heater board 301b that forms the edge faces of ink flow paths, and the outer side of front end of ceiling plate 305b as well. In this respect, the edge faces of ink flow paths 301b and 305b are structured to protrude from the surface of front plate portion 311b by several tens of μm to several hundreds of μm approximately.
Next, the orifice plate 306 is bonded by use of bonding agent or some other bonding means to the edge faces of ink flow paths 301b and 305b which are formed to protrude by the heater board 301 and the ceiling plate 305. At this juncture, the surface of the front plate portion 311b is formed to be retracted from the ink flow path edge faces 301b and 305b as described earlier so as not to impede bonding of the orifice plate 306 and the ink flow edge faces 301b and 305b. 
Then, in the last process that follows, bonding agent or sealant is poured into the gap (the stepped portion of several tens of μm to several hundreds of μm between the front plate portion 311b and the ink flow path edge faces 301b and 305b) formed between the area where no discharge ports 306a are arranged on the backside of the orifice plate 306 and the front plate portion 311b, thus completing the bonding of orifice plate 306.
In this way, the assembling process of the liquid discharge recording head 315 is completed.
Also, as another conventional liquid discharge recording head, there exists the structure in which, as shown in FIG. 69, the central portion of front face of an orifice cover 312 is removed, and additionally arranged to cover only four sides of orifice plate 306.
In a general case where a liquid discharge recording head is structured so that the orifice plate is bonded to the opening face of liquid flow paths (nozzles) of a recording head, the ink discharge face is cleaned by the wiping operation of recovery device as shown in FIG. 70, and then, as in the wiping operation b shown in FIG. 70, the edge portion of the wiping blade 321 is in contact with the orifice plate edge portion 306c as if to draw it. As a result, the orifice plate 306 is liable to be peeled off from the recording head 315 at the edge portion 306c. Also, the leading end of the wiping blade 321 slidably rubs the facing end 306b of the orifice plate 306. As a result, there is a possibility that peeling off occurs at the edge portion of the orifice plate other than the edge portion at 306c by the repetition of wiping operation.
If the edge portion of orifice plate should be peeled off even slightly, it advances further by repetition of wiping operations to follow, and the recording head is damaged beyond recovery ultimately.
In order to avoid such problem as this, the structure is arranged as shown in FIG. 69 to provide an orifice cover 312 to cover the four sides of an orifice plate 306. With this structure, however, the area where capping means is allowed to abut against for suction recovery becomes relatively narrower. As a result, there is a need for the use of highly precise component as capping means in order to make the capping operation more accurately. Then, if it is intended to make the area larger where capping means abuts against in such structure having the additional orifice cover 312 as it is, the recording head components should become relatively larger to increase both costs and the area occupied by the recording apparatus as a whole which is made larger after all.
Further, the structure in which the orifice cover 312 is added creates a step between the orifice cover 312 and the orifice plate 306. As a result, remaining liquid on the orifice plate 306 tends to form a pool on the corners of such step when wiping is performed by use of the blade 321 or there is a fear that uneven wiping takes place due to the insufficient contact which is caused by the vibration or jump over of the blade 321. Furthermore, there is a possibility that the blade 321 is damaged due to the one-sided contact of the blade 321 with the step between the orifice cover 312 and orifice plate 306. Thus, this structure presents the problem of reliability, too.
Also, the structure that does not use any orifice cover may make it possible to design a method for regulating the slidably rubbing area between the wiping blade and the face of the orifice plate by making the movable range of the wiping blade narrower so that the wiping blade is not hooked by the edge portion of the orifice plate. In this method, however, it is firstly needed to arrange the structure so that the wiping blade is made detractable from the face of orifice plate, which makes the costs of wiping device higher inevitably. Secondly, this structure brings about such unfavorable condition as to return dust particles (such as dust, powdered paper, paper fluffs) or excessively viscous ink (ink the volatile component of which has been evaporated), which are collected by the rubbing face of blade by wiping and adhere to it, onto the face of the orifice plate. In other words, there is a fear that the dust particles or excessively viscous ink collected by the rubbing face of the blade by wiping and adhere to it are transferred and returned to the face of the orifice plate when the wiping blade is retracted or rubbed again to adhere to the face of orifice plate.
As described above, the method that uses the orifice cover or the method for regulating the area where the wiping blade and face of orifice plate are slidably rubbed each other is not very advisable.